Rubble foundations of a small square, stone built structure, measuring c. 3.5m x 3.5m externally, with the internal space c. 1.5m squared. There is an entrance on the south side. Access is via a track (NPRN 245,050) leading up from Nant-Y-Brain mine. It's location at a distance from the rest of the mine workings, and its' small size may suggest that it was an explosives magazine.

Helen Whitear and Duncan Schlee, Dyfed Archaeological Trust, 2008.